High intensity focused ultrasound (HIFU) has gained significant ground as a promising, non-ionizing, non-invasive method of the treatment for a variety of cancers. Although clinical trials have demonstrated its unique advantages, a broad scope of HIFU application in cancer therapy is still limited by the stringent inclusion criteria in patient selection. Furthermore, HIFU as it is currently employed cannot treat distant metastasis, and it may lead to local recurrence in cases of incomplete tissue necrosis. In light of these shortcomings, it is important to explore novel implementation strategies of HIFU within a larger framework of multi-treatment modalities for cancer therapy. Such combinational strategies may increase the effectiveness and application spectrum of HIFU as well as the overall outcome of existing cancer treatment modalities. Recent investigations have demonstrated encouraging results of a HIFU-elicited anti-tumor immune response. HIFU may induce changes in the tumor microenvironment that are conducive for stimulating a tumor specific immune response which can be exploited through a synergistic combination with other established cancer treatment modalities for improved efficacy. In preliminary studies, we have shown in vivo that mechanical lysis of tumor cells with HIFU yields an increase in dendritic cell (DC) infiltration to the tumor with subsequent migration to the draining lymph nodes, a critical step in eliciting an anti-tumor immune response. Also, in a B16 murine melanoma model, we have observed a decrease in metastasis rates when subcutaneous tumors were treated with HIFU two days before surgical resection. In contrast, when surgery was performed immediately following HIFU treatment, thus eliminating the possibility of DC infiltration and maturation at the damaged tumor site, there was no observed significant difference in metastasis rates. While current HIFU clinical trials are mainly focused on producing localized thermal ablation of the primary tumor, there is conceptually an even greater potential for utilizing HIFU as an adjuvant therapy within the large multimodality framework of cancer therapy. For example, HIFU may be implemented as an outpatient pretreatment to suppress the primary tumor growth while stimulating concomitantly an anti-tumor immune response before surgery, radiotherapy, and/or chemotherapy for the large population of cancer patients who may not be eligible for HIFU monotherapy. Furthermore, combinations of HIFU with other immunotherapeutic strategies such as dendritic cell or cytokine-based vaccines may yield improved responses through synergistic interactions. PUBLIC HEALTH RELEVANCE: The objective of this exploratory R21 proposal is therefore two-fold: 1) To optimize HIFU treatment parameters to maximize the elicited anti-tumor immune response in a B16 melanoma mouse tumor model, and 2) to investigate the synergistic combination of HIFU with dendritic cell and GM-CSF injections in suppressing distant metastasis in the melanoma mouse model post-surgical resection of the primary tumor.